Enhance if-conversion for automatic arrays

Automatic arrays that are not address-taken should not be subject to
store data races.  This applies to OMP SIMD in-branch lowered
functions result array which for the testcase otherwise prevents
vectorization with SSE and for AVX and AVX512 ends up with spurious
.MASK_STORE to the stack surviving.

This inefficiency was noted in PR111793.

I've introduced ref_can_have_store_data_races, commonizing uses
of flag_store_data_races in if-conversion, cselim and store motion.

	PR tree-optimization/111793
	* tree-ssa-alias.h (ref_can_have_store_data_races): Declare.
	* tree-ssa-alias.cc (ref_can_have_store_data_races): New
	function.
	* tree-if-conv.cc (ifcvt_memrefs_wont_trap): Use
	ref_can_have_store_data_races to allow more unconditional
	stores.
	* tree-ssa-loop-im.cc (execute_sm): Likewise.
	* tree-ssa-phiopt.cc (cond_store_replacement): Likewise.

	* gcc.dg/vect/vect-simd-clone-21.c: New testcase.

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